JPH06347284A - Strain gauge type converter and initial value variation detecting method thereof - Google Patents

Abstract

PURPOSE:To provide a converter which has a converter which has a function to allow the detection of a variation of an initial value singly despite a simple and inexpensive construction and a method which enables the detection or removal of the variation of the initial value simply and in a short time from the ground even with the converter buried. CONSTITUTION:In strain gauges, two gauge element patterns are made on the same substrate under the same conditions and various characteristics of the strain gauges are regarded identical. A first bridge circuit B1 is made up of first and fourth active gauges Ra1-Ra4 attached to a strain developing part of a strain developing body which causes all strains. A second bridge circuit B2 is fifth and sixth active gauges Ra5 and Ra6 attached to the strain developing part and other two sheets of dummy gauges Rd1 and Rd2 attached to a rigid part at positions therenear among four sheets of strain gauges. Thus, the variation of the initial value can be detected based on outputs of the second bridge circuit B2 and the first bridge circuit B1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain gauge type transducer and a method for detecting an initial value fluctuation amount of a strain gauge type transducer. More specifically, the present invention relates to a strain caused by receiving physical quantities such as pressure, displacement, load and acceleration. A strain gauge type transducer attached to the strain generating part of a strain generating body, which converts a physical quantity into an electric quantity by a strain gauge showing a resistance change corresponding to the strain, and an initial value fluctuation amount generated in the strain gauge type converter. It relates to a method of detecting.

[0002]

2. Description of the Related Art As a strain gauge type physical quantity-electric quantity converter (hereinafter sometimes referred to simply as "converter"), various physical quantities such as pressure, displacement, load, acceleration and the like have been used in the past. Signal transducers, pressure transducers, displacement transducers, load transducers, acceleration transducers and the like are widely used.

Such a conventional transducer is attached to the strain-generating portion of a strain-generating body which receives a physical force acting through the sensing portion and deforms according to the force. A strain gauge showing a resistance change according to the deformation, a cable for transmitting an electric signal output of the strain gauge to an external measuring instrument, and a casing member for cutting off the strain gauge from the outside are constituted as main constituent members. Has been done.

In the conventional converter thus constructed, in order to increase the minute resistance change of the strain gauge and to eliminate the error due to temperature compensation and parasitic strain,
A Wheatstone bridge circuit (herein simply referred to as "bridge circuit") is used.

[0005]

However, in the converter having such a bridge circuit configuration, the material of the strain gauge, the base, the adhesive, etc. change with time during long-term use. A change in the initial value (also referred to as "output without load" or "initial value") occurs.

[0006] More specifically, as a factor of the change over time of the strain gauge, the resistance value of the resistance element changes due to the release of processing strain, or the volume of the adhesive or the gauge base swells due to moisture absorption. Mechanical factors that give rise to strain, the insulation of the gauge base and the adhesive deteriorates, and it is added in parallel to the gauge resistance. A chemical factor that causes corrosion and changes in resistance can be considered.

Such fluctuations in the initial value are mixed in the physical quantity to be measured by the strain gauge, and it is very difficult to separate them. Therefore, the accuracy of the measured value is lowered and It hindered reliability. In particular, in the case of instruments actually used for construction management or maintenance at the site of civil engineering construction, especially converters used buried, it is almost impossible to dig up and inspect, so the initial value It is impossible to detect the fluctuation amount of
In other words, there is no established method for confirming the reliability of the measurement data of the embedded converter.

The present invention has been made in view of the above-mentioned circumstances. A first object of the present invention is to detect the initial value fluctuation amount for each converter although the structure is simple and inexpensive. It is to provide a strain gauge type transducer having a function.

A second object of the present invention is to detect the initial value fluctuation amount or remove the initial value fluctuation amount from the ground even in a buried state easily and in a short time to obtain the true value of the physical quantity. An object of the present invention is to provide a method for detecting an initial value variation amount of a strain gauge type transducer that can obtain corresponding measurement data.

[0010]

In order to achieve the first object, the present invention is attached to a strain generating portion of a strain generating body which receives a physical quantity such as pressure, displacement, load or acceleration to generate strain. In a strain gauge type converter for converting the physical quantity into an electric quantity by a strain gauge showing a resistance change corresponding to the strain, first to fourth parts attached to the strain generating part of the strain generating body.
And the strain gauge characteristics of the first active gauge such as strain output characteristics, aging characteristics, gauge ratio and temperature characteristics, which are attached to positions that can be regarded as substantially the same as the first active gauge. A fifth active gauge that can be considered to be substantially the same, and a strain output characteristic, a time-dependent change characteristic, a gauge ratio of the second active gauge that is attached to a position that can be considered to be substantially the same position as the second active gauge. 6th strain gauge characteristics such as temperature characteristics can be regarded as substantially the same
Of the active gauge and the third active gauge, and is attached to at least the rigid body portion of the strain-generating body in the vicinity of the third active gauge and substantially not causing strain due to the physical quantity.
First dummy gauge having a time-varying characteristic that can be considered to be substantially the same as the time-varying characteristic of the active gauge described above, and the strain-generating body near the fourth active gauge that does not substantially cause strain due to the physical quantity. A second dummy gauge that is attached to the rigid body portion and has at least a time-dependent change characteristic that can be regarded as substantially the same as the time-dependent change characteristic of the fourth active gauge. Forming a first bridge circuit,
A second bridge circuit is formed by the fifth and sixth active gauges and the first and second dummy gauges, and a strain output component corresponding to the physical quantity based on the outputs of the first and second bridge circuits. It is characterized in that it is configured so as to be able to separate the above-mentioned time-dependent change component of the initial value.

Further, in order to achieve the first object, the present invention responds to the strain by being attached to a strain generating portion of a strain generating body which generates strain by receiving physical quantities such as pressure, displacement, load and acceleration. In a strain gauge type converter that converts the physical quantity into an electric quantity by a strain gauge showing the resistance change,
First to fourth active gauges attached to the strain generating portion of the strain generating body, and the strain generating body which is in the vicinity of each of the first to fourth active gauges and does not substantially generate strain due to the physical quantity. The first to fourth dummy gauges, which are attached to the rigid body portion in pairs and have a time-varying characteristic that can be regarded as substantially the same as the time-varying characteristic of the active gauge forming at least a pair. ~ Forming a first bridge circuit with a fourth active gauge,
~ A second bridge circuit is formed with a fourth dummy gauge, and a strain output component corresponding to the physical quantity and an initial value fluctuation output component associated with the change over time are formed based on the outputs of the first and second bridge circuits. It is characterized in that it is configured so that it can be detected separately.

Further, in order to achieve the above-mentioned second object, the present invention is attached to a strain-generating portion of a strain-generating body which receives a physical quantity such as a pressure, a displacement, a load, an acceleration or the like to generate a strain, and corresponds to the strain. A method for detecting an initial value fluctuation amount of a strain gauge type converter that converts the physical quantity into an electric quantity by a strain gauge showing a resistance change, the first to the first attached to the strain generating portion of the strain generating body. No. 4 active gauge forms a first bridge circuit and is attached to a position that can be regarded as substantially the same position as the first active gauge, and has a strain output characteristic, a aging characteristic, and a gauge of the first active gauge. The fifth active gauge whose strain gauge characteristics such as rate and temperature characteristics can be regarded as substantially the same and the position which can be regarded as substantially the same position as the second active gauge are added. In the vicinity of the third active gauge and the sixth active gauge which can be regarded as substantially the same strain gauge characteristics such as strain output characteristics, aging characteristics, gauge ratio and temperature characteristics of the second active gauge. A first dummy that is attached to the rigid portion of the strain-generating body and that does not substantially cause strain due to the physical quantity, and that has at least a time-dependent change characteristic that can be regarded as substantially the same as the time-dependent change characteristic of the third active gauge. The gauge and the fourth active gauge are attached to the rigid body portion of the strain generating body in the vicinity of the fourth active gauge and do not substantially generate strain due to the physical quantity, and are considered to be substantially the same as the aging characteristics of at least the fourth active gauge. A second bridge circuit is formed with the obtained second dummy gauge, and the output of the second bridge circuit is doubled. By subtracting the output of said first bridge circuit from the one in which and obtains the amount of variation of the initial value due to the aging.

Furthermore, in order to achieve the above-mentioned second object, the present invention applies the strain to a strain-causing portion of a strain-generating body which receives a physical quantity such as pressure, displacement, load, acceleration or the like and causes strain. A method for detecting an initial value fluctuation amount of a strain gauge type converter for converting the physical quantity into an electric quantity by a strain gauge showing a corresponding resistance change, wherein the first to the first strains attached to the strain generating portion of the strain generating body. A first bridge circuit is formed with a fourth active gauge, and the first to fourth
Of the active gauge, which is substantially the same as the time-varying characteristics of the active gauges that are attached in pairs to the rigid portions of the flexure element that do not substantially cause strain due to the physical quantity and that are attached at least in pairs. A second bridge circuit is formed with the first to fourth dummy gauges that can be regarded as time-dependent characteristics, and the time-dependent change is obtained by subtracting the output of the second bridge circuit from the output of the first bridge circuit. It is characterized in that the initial value fluctuation amount due to is detected and removed to obtain an output corresponding to the physical quantity.

[0014]

The first bridge circuit of the strain gauge type transducer configured as described above has four active elements attached to the strain-generating portion in order to convert the amount of strain corresponding to the physical quantity into the amount of electricity. It is formed with a gauge.

On the other hand, the second bridge circuit is made insensitive to the two physical gauges attached to the strain-flexing part in order to convert the strain amount corresponding to the physical amount into the electrical amount and the physical amount to be measured, It is formed with two dummy gauges attached to the rigid body so as to be sensitive to changes over time.

Here, the output component corresponding to the physical quantity to be measured of the first bridge circuit is K1, the output component corresponding to the change over time of the strain gauge material, the gauge base, the adhesive, etc. is D1, and the output component corresponding to the creep. Is C1, the output eo1 of the first bridge circuit can be expressed as eo1 = K1 + D1 + C1 (1)

If K2 is the output component corresponding to the physical quantity to be measured of the second bridge circuit, D2 is the output component corresponding to the above-described change over time, and C2 is the output component corresponding to the creep, the strain detection function is half. Since it is a bridge, the components of K2 and C2 related to the strain amount are 1 /
Since the condition for D2 is considered to be the same, the output eo2 of the second bridge circuit should be expressed as eo2 = (K2 / 2) + D2 + (C2 / 2) (2). You can

Therefore, if the equation (2) is doubled and the equation (1) is subtracted, 2 {(K2 / 2) + (D2) + (C2 / 2)}-{K1 + D1 + C1} = K2 + 2D2 + C2-K1 -D1-C1 = (K2-K1) + (2D2-D1) + (C2-C1) = D2 or D1 ... (3). What is required is that the strain gauges of the first bridge circuit and the strain gauges of the second bridge circuit have at least pairs of strain gauges attached to each other at or near positions at which they can be regarded as substantially the same, and strain output characteristics , K1 = K2, D1 = D, since the ones whose aging characteristics, gauge factor and temperature characteristics can be regarded as substantially the same are used.
2, C2 = C1, and as shown in (3) above, the output component D1 or D2 caused by the change over time is obtained.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 is a vertical cross-sectional view of a pore water pressure gauge which is an example of the strain gauge type transducer according to the first embodiment of the present invention.

In the figure, 1 is a casing,
On one end (lower end in the figure) side, there is provided an opening 1d formed by forming counterbored holes having different diameters to form first to third step portions 1a, 1b, 1c, and the opening end thereof. 1
A female screw 1e is formed inside d, and a small-diameter hole 1f and a counterbore hole 1g having a larger diameter than that are formed on the other end side (upper end side in the figure). A female screw 1h is formed at the open end of the hole 1g.

Then, in the first step 1a in the opening 1d of the casing 1, conductive pins 2a, 2a are provided in an airtight manner so as to penetrate from one surface side to the other surface side and a terminal with an airtight terminal 2b. Although not shown, the plate 2 is attached by screws.

To the second step portion 1b in the opening 1d of the casing 1, the opening end (lower end in the figure) of the thick-walled cylindrical portion 3a of the flexure element 3 is fixed in an airtight manner by welding.

Further, one or a plurality of filters 4 are locked to the third step portion 1c in the opening 1d of the casing 1, and the ring nut 5 screwed to the female screw portion 1e in a locked state. Is fixed by.

On the other hand, the small-diameter hole 1 at the other end of the casing 1
In f, the cord 6 in which the core wires 6a, 6a ... Are connected to the conductive pins 2a, 2a ... Is inserted, and the rubber bush 7 is inserted in the gap between the cord 6 and the counterbore 1g of the casing 1. It is tightened by the ring nut 8 to prevent water from entering from the outside.

On the inner side surrounded by the thick-walled cylindrical portion 3a of the strain-flexing body 3, there is provided a strain-flexing portion 3b formed in the shape of a thin diaphragm, and the central region thereof is thickened. The central thick rigid body portion 3c is provided, and the first to sixth active gauges Ra1 to Ra1 are respectively provided at the central portion and the peripheral portion on the non-pressure receiving surface side (upper surface in the drawing) of the strain-flexing portion 3b.
Ra6 is deposited and attached by, for example, a sputtering method.

On the non-pressure receiving surface side of the thick central rigid body portion 3c of the strain generating element 3, there is substantially no strain due to the water pressure as the physical quantity to be measured, and the active gauge R of the strain generating element 3 is
The first and second dummy gauges Rd1 and Rd2 receive the same temperature conditions and humidity conditions as those of a1 to Ra6.
Similarly, it is formed by the sputtering method under the same conditions at the same time as the first to sixth active gauges Ra1 to Ra6.

These strain gauges Ra1 to Ra6, R
The gauge tabs d1 and Rd2 and the corresponding conductive pins 2a, 2a ...
Connected by.

Next, with reference also to FIGS. 1, 3, 4, and 5, a strain gauge and a strain gauge attached to the strain generating portion of the strain gauge, and a bridge circuit formed by the strain gauge. The configuration will be described in detail.

FIGS. 3 and 4 are a longitudinal sectional view and a plan view showing a strain element 3 in FIG. 2 and a state in which a strain gauge is attached to the strain element of the strain element.

FIG. 5 is a plan view partially showing the structure of a pair of gauge patterns formed on the surface of the strain-flexing portion.

FIGS. 6 and 7 are a longitudinal sectional view and a plan view showing an example of the configuration of the flexure element different from those in FIGS. 3 and 4.

In these figures, the flexure element 3 has a substantially cylindrical shape with one end (the lower end in the figures) opened, and is formed thick to provide a large rigidity to a thick cylindrical portion 3a.
And a strain-flexing portion 3b that is thin and has flexibility
And a central thick rigid body portion 3c in which the central region of the strain-flexing portion 3b is formed thick and is provided with great rigidity.

The strain-flexing portion 3b and the thick central rigid body portion 3c.
5, the same gauge patterns 12b and 12c are formed on one substrate (gauge base) 12a as shown in FIG.
Are simultaneously formed by the same material, for example, by a sputtering method, so that their grid portions 12e are close to each other so as to enter the meandering concave portions 12d on the opposite side and the respective sensitive axes 12f face the same direction. The double strain gauge 12 thus formed is attached.

Two gauge elements are formed in this double type strain gauge 12, but basically, in this embodiment, these two gauge elements are respectively incorporated in one sides of different bridge circuits.

That is, in FIG. 3 and FIG.
In the case of the double type strain gauge 12-1 attached to the two portions of the thick cylindrical portion 3a close to b, one gauge pattern 12b is used as the first active gauge Ra1 and the other gauge pattern 12c is the fifth gauge pattern 12c. In the case of the double type strain gauge 12-3, one gauge pattern 12b is used as the third active gauge Ra3 and the other gauge pattern 12c is used as the first gauge. It is used as the dummy gauge Rd1 of.

Further, in FIGS. 3 and 4, in the case of the double type strain gauge 12-2 attached to two portions of the strain generating portion 3b near the central thick rigid body portion 3c, one of the gauge patterns 12b is the second. , The other gauge pattern 12c is used as the sixth active gauge Ra6, and in the case of the double type strain gauge 12-4, one of the two gauge patterns 12b and 12c is used. Only the fourth active gauge Ra4 is used.

3 and 4, in the case of the double type strain gauge 12-5 attached to the portion on the non-pressure receiving surface side of the thick-walled cylindrical portion 3a of the flexure element 3, two gauge patterns 1 are used.
Only one of 2b and 12c is used as the first dummy gauge Rd1, and the double type strain gauge 1 attached to the central thick rigid body portion 3c of the strain generating body 3 is used.
In the case of 2-6, two gauge patterns 12b and 12c
Only one of them is used as the second dummy gauge Rd2.

The above double type strain gauges 12-1 to 12-1
2-6 use the thing formed simultaneously on the same conditions.

The double type strain gauges 12-1 to 12-6 attached to the strain generating portion 3b and the central thick rigid portion 3c of the strain generating body 3 in this way are connected as shown in FIG. Two bridge circuits are formed which receive a common bridge power supply voltage. That is, the first bridge circuit B
1 is formed by connecting the first active gauge Ra1 and the third active gauge Ra3 to the opposite sides, and connecting the second active gauge Ra2 and the fourth active gauge Ra4 to the adjacent opposite sides. There is.

In the second bridge circuit B2, the fifth active gauge Ra5 and the first dummy gauge Rd1 are connected to the opposite sides, and the sixth active gauge Ra6 and the second dummy gauge Rd2 are adjacent to each other. It is formed so as to be connected to the opposite side.

These two bridge circuits B1 and B
2, the consideration is given so that the strain gauges connected to the corresponding bridge sides are paired with each other and the environmental conditions (arrangement conditions) and the strain gauge characteristics can be regarded as substantially the same.

That is, the first active gauge Ra1
And a fifth active gauge Ra5, and a second
Active gauge Ra2 and sixth active gauge R
The pair with a6 is formed by forming two gauge patterns close to each other on the same substrate by sputtering to attach them to positions that can be regarded as substantially the same position, and the output characteristics of the strain gauges of each pair. The aging characteristics, the gauge factor, and the temperature characteristics are also set to the extent that they can be regarded as substantially the same.

The pair of the third active gauge Ra3 and the first dummy gauge Rd1 and the pair of the fourth active gauge Ra4 and the second dummy gauge Rd2 are not the same substrate, but under the same manufacturing conditions. By using the manufactured strain gauges 12-3 and 12-5 and 12-4 and 12-6, active gauges that use at least those whose aging characteristics can be regarded as substantially the same and which make up each pair are used. And the dummy gauge are attached to the portion of the strained portion 3b and the central thick rigid portion 3c in the vicinity thereof.

Next, the operation of the pore water pressure gauge having such a structure will be described.

The pore water pressure gauge measures, for example, pore water pressure due to waves of soil particles in the ground or ocean structures.
When this is buried in soil or the like, pore water passes through the filter 4 and deforms the diaphragm strain element 3b by the pore water pressure, and the deformation amount of the strain element 3b is measured by the strain gauges 12-1 to 12-1.
12-4 (active gauges Ra1 to Ra4) converts it into an electric resistance value, and this is converted into a gauge lead 9, a conductive pin 2a,
The basic operation of outputting to the external strain measuring device through the cord 6 containing the core wire 6a sequentially is the same as that of the conventional pore water pressure gauge.

However, the pore water pressure gauge according to the present invention is different from the conventional one in that it has a function of detecting a so-called initial value fluctuation (zero drift) amount.

The two initial value variation detecting functions will be described in detail below. The active gauges Ra1 to Ra6 and the dummy gauge Rd attached to the strain-flexing portion 3b and the central thick-walled rigid body portion 3c of the strain-flexing body 3 of the pore water pressure gauge, respectively.
1 and Rd2 are connected as shown in the circuit diagram of FIG. 1 to form two bridge circuits B1 and B2.

That is, in the first bridge circuit B1, all four active gauges R attached to the strain-flexing portion 3b in order to convert the pore water pressure, which is a physical quantity to be measured, into an electric quantity.
It is formed by a1 to Ra4.

On the other hand, the second bridge circuit B2 includes two active gauges Ra5 and Ra6 attached to the strain-flexing portion 3b so as to convert the strain amount corresponding to the pore water pressure, which is a physical amount, into an electric amount. 2 attached to the thick-walled cylindrical portion 3a and the central thick-walled rigid portion 3c so as to be insensitive to the pore water pressure to be measured and sensitive to the change over time of the strain gauge.
It is formed with the dummy gauges Rd1 and Rd2.

Here, the output component corresponding to the pore water pressure of the first bridge circuit B1 is caused by K1, the output component corresponding to the change with time of the strain gauge material, the gauge base, the adhesive, etc. is caused by D1, and the creep is caused. When the output component is C1, the output eo1 of the first bridge circuit B1 can be expressed as eo1 = K1 + D1 + C1 (1).

The output component corresponding to the pore water pressure of the second bridge circuit B2 is K2, the output component caused by the change with time is D2, and the output component caused by the creep is C.
In the case of 2, the latter second bridge circuit B2 is a half bridge as a strain detecting function, and therefore the output components K2 and C2 related to the strain amount are 1 /
It is considered that the output component becomes 2 and the output components due to the above-mentioned change with time are the same.

Therefore, the output e of the second bridge circuit B2
o2 can be expressed as eo2 = (K2 / 2) + D2 + (C2 / 2) ... (2).

Therefore, when the equation (2) is multiplied by 2 and the equation (1) is subtracted, 2 {(K2 / 2) + D2 + (C2 / 2)}-{K1 + D1 + C1} = K2 + 2.D2 + C2-K1-D1 -C1 = (K2-K1) + (2 · D2-D1) + (C2-C1) ∴2 · eo2-eo1 = D2 or D1 (3).

What is important is that, as described above, the first active gauge Ra1, the fifth active gauge Ra5 and the second active gauge Ra2, which form a pair of the first bridge circuit B1 and the second bridge circuit B2, respectively. The sixth active gauge Ra6 and the sixth active gauge Ra6 are attached to positions that can be regarded as substantially the same, and strain output characteristics, aging characteristics, gauge ratio, temperature characteristics, and the like can be regarded as substantially the same. The third active gauge Ra3 and the first dummy gauge Rd1 and the fourth active gauge Ra4 and the second dummy gauge Rd2
Are attached to the strain-flexing portion 3b and the rigid body portion 3c, respectively, but can be regarded as being substantially the same in environmental conditions because they are disposed in the vicinity of each other, and the temporal change characteristics and other characteristics are also substantially the same. Since it can be regarded as K1 = K2, D1 = D2, and C2 = C1 as a result, the output component caused by the change over time, that is, The initial value fluctuation amount D1 = D2 is obtained.

This initial value fluctuation amount D1 (D2) can be calculated using an analog calculation circuit or after converting the analog amount into a digital amount using a calculation function such as a microcomputer. By subtracting the calculated initial value fluctuation amount from the value output from the first bridge circuit B1, it is possible to obtain measurement data that truly corresponds to the pore water pressure that is the measured physical quantity.

Further, the output of the second bridge circuit B2 is set to 2
By checking whether the doubled data is the same as the output of the first bridge circuit B1, it is possible to check the reliability of the output value of the first bridge circuit B1.

It should be noted that it is desirable to be able to determine how much the creep amount indicated by C above is, but at present, no means has been found to separate it from the measured value. However, regarding the creep, by adopting the above-described method of forming a gauge pattern by the sputtering method, the creep can be made so small that there is no problem even if it is actually ignored.

The present invention is not limited to the ones described in detail in the above-mentioned embodiments, and various modifications can be made without departing from the scope of the invention.

For example, as shown in FIGS. 6 and 7, the structure of the flexure element is formed by forming two slits 10e and 10f in a symmetrical position with the center narrowed in the flexure portion 10b. Forming a beam-shaped strain-generating portion 10b, and fixing the pressure-receiving diaphragm 11 by welding so as to close the opening end (lower end in the figure) of the strain-generating body 10 in an airtight manner, and centering the pressure-receiving diaphragm 11 And central thick rigid body 10
Alternatively, the force transmission rod 10d may be connected to the position c.

In this case, the double type strain gauge 12-1 composed of the first and fifth active gauges Ra1 and Ra5 is attached to the portion of the strain-flexing portion 13b near the thick-walled cylindrical portion 13a, and the second and sixth strain gauges 12-1 are attached. Active gauge Ra
Double strain gauge 12-2 consisting of 2 and Ra6
Is attached to a portion of the strain-flexing portion 13b near the central thick-walled rigid body portion 10c.

The double strain gauge 12-3, which is the third active gauge Ra3, and the double strain gauge 12-5, which is the first dummy gauge Rd1, are located closer to the thick cylindrical portion 10a of the strain generating portion 13b. They are attached to the portion and the thick-walled cylindrical portion 10a, respectively.

The double strain gauge 12-4, which is the fourth active gauge Ra4, and the double strain gauge 12-6, which is the second dummy gauge Rd2, are closer to the center thick-walled rigid body portion 10c of the strain generating portion 10b. And the central thick-walled rigid body portion 10c.

In the case of such a configuration, the single-character beam-shaped strain generating portion 10b excellent in linearity of the pressure-strain output characteristic is provided.
Is advantageous in that

Further, the flexure element having the structure shown in FIGS. 8 and 9 is also applicable to the present invention.

8 and 9, the flexure element 1 in this case is shown.
3 is different from the flexure element 3 shown in FIG. 2, FIG. 3, FIG.
There is no central thick-walled rigid body portion 3c, and there is a thick-walled cylindrical portion 13a having a cylindrical shape with one end open, and a strain-flexing portion 13b having a cylindrical closed end side formed in a thin diaphragm shape. Has two circular holes having different diameters and is provided with a stepped portion 13c.

A double strain gauge 12-1 composed of a first active gauge Ra1 and a fifth active gauge Ra5 is attached to the central portion of the strain-flexing portion 13b of the strain-flexing body 13 thus configured. ing.

Similarly, in the central portion of the strain-flexing portion 13b,
A double strain gauge 12-2 composed of a second active gauge Ra2 and a sixth active gauge Ra6 is attached.

Further, at two locations near the thick-walled cylindrical portion 13 of the strain-flexing body 13b, a double-type strain gauge 12-3 and a fourth strain gauge 12-3 used as a third active gauge Ra3 are provided.
The double type strain gauge 12-4 used as the active gauge Ra4 is attached.

On the thick rigid body portion 13a in the vicinity of the double type strain gauges 12-3 and 12-4, the double type strain gauge 12-5 and the second dummy gauge Rd1 used as the first dummy gauge Rd1, respectively. A double type strain gauge 12-6 used as Rd2 is attached.

The strain gauges thus attached are connected in the circuit configuration shown in FIG. 10 to form two bridge circuits B1 and B2.

This bridge circuit configuration is different from the circuit shown in FIG. 1 in that two pairs of second active gauges Ra are used.
The double strain gauge 12-2 including the second active strain gauge Ra6 and the sixth active gauge Ra6 is inserted and connected not to the side adjacent to the double strain gauge 12-1 having the same configuration but to the opposite side, and to the adjacent side. Is different in that the double strain gauges 12a-3 and 12-5 are inserted and connected.

FIGS. 11 and 12 relate to the second embodiment, and the point where the second bridge circuit B2 is entirely formed by a dummy gauge and the strain gauge is not a double type but a single type. The difference is that it is done.

That is, the first active gauge Ra1 and the third active gauge Ra3 are attached to two portions of the strain-flexing portion 3b near the thick-walled cylindrical portion 3a, and on the thick-walled cylindrical portion 3a in the vicinity thereof. The first dummy gauge Rd1
And a third dummy gauge Rd3 is attached.

A second active gauge Ra2 and a fourth active gauge Ra4 are attached to two portions of the strain-flexing portion 3b near the central thick-walled rigid body portion 3c. On the 3c, the second dummy gauge R
d2 and the fourth dummy gauge Rd4 are attached.

Among the strain gauges attached to the strain-flexing body 3 in such an arrangement relationship, as shown in FIG. 11, the active gauges Ra1 to Ra4 form a bridge circuit B1 for obtaining physical quantity measurement data. And dummy gauge Rd
1 to Rd4 form a bridge circuit B2 for separating and detecting an initial value variation component caused by a change with time of the strain gauge, regardless of strain detection.

As described above, the dummy gauges Rd1 to Rd4 are manufactured under the same conditions as the active gauges Ra1 to Ra4, and can be regarded as substantially the same, and are used under the environment. By subtracting the output of the second bridge circuit B2 from the output of the bridge circuit B1, it is possible to obtain measurement data that accurately corresponds to the physical quantity to be measured.

13 and 14 show modified examples of the flexure element when the present invention is applied to a load converter or an acceleration converter.

In the flexure element 3 according to this modified example, the slits 3d and 3f are formed so as to sandwich the central thick rigid body section 3c, and the so-called one-character beam-shaped flexure section 3b is provided. 3 and 4 and the like.

Since the attachment position of the strain gauge and the circuit connection structure can be understood from the above description, the description thereof will be omitted.

In addition to the above, by increasing the number of strain gauges, for example, a plurality of strain gauges for exhibiting the same function are attached and connected in series to the same side of the bridge circuit. May be.

The type of transducer to which the present invention can be applied is not limited to the pore water pressure gauge and the load transducer described above, and the displacement transducer, acceleration transducer, torque transducer, and the like can be attached to the strain-flexing portion. It can be applied to all converters of the type in which a physical quantity is extracted as an electric quantity by forming a bridge circuit with the strain gauges.

[0083]

As described in detail above, according to the present invention, there is provided a strain gauge type transducer having a simple and inexpensive structure and having a function of detecting the initial value variation by the transducer alone. can do.

Further, according to the method of the present invention, the initial value fluctuation amount is detected from the ground easily and in a short time even if it is buried, and the initial value fluctuation amount is removed to obtain the true value of the measured physical quantity. It is possible to provide a method for detecting an initial value variation amount of a strain gauge type transducer that can obtain corresponding measurement data.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a bridge circuit used in a pore pressure gauge as a strain gauge type transducer according to the present invention.

FIG. 2 is a vertical cross-sectional view showing the structure of a pore water pressure gauge according to the present invention.

FIG. 3 shows a configuration of a strain element of the pore water pressure gauge shown in FIG.
It is sectional drawing shown with the XX line arrow direction cross section of FIG.

FIG. 4 is a plan view of FIG. 3, showing a positional relationship of attachment of strain gauges.

FIG. 5 is a plan view showing a part of the configuration of a gauge pattern of a double type strain gauge attached to a strain generating element of the strain gauge type transducer according to the present invention.

FIG. 6 is a cross-sectional view showing a vertical cross-sectional structure of a flexure element different from those shown in FIGS. 3 and 4.

7 is a plan view of the flexure element shown in FIG.

8 is a vertical cross-sectional view of a flexure element different from those shown in FIGS. 3 and 6. FIG.

9 is a plan view of the flexure element shown in FIG. 8. FIG.

10 is a circuit diagram showing a circuit configuration of a strain gauge attached to the strain generating element shown in FIGS. 8 and 9. FIG.

FIG. 11 is a circuit diagram showing a circuit configuration of a second embodiment according to the present invention.

FIG. 12 is a plan view showing a configuration of a flexure element according to the example.

FIG. 13 is a vertical cross-sectional view of a flexure element when the present invention is applied to a load converter.

14 is a plan view of the flexure element shown in FIG.

[Explanation of symbols]

 1 Casing 1a-1c 1st-3rd step part 1d Opening part 1e Female screw part 1f Small diameter hole 1g Counterbore hole 1h Female screw 2 Terminal plate 2a Conductive pin 2b Airtight terminal 3 Strain element 3a Thick cylindrical part 3b Strain Part 3c Center thick rigid part 3d, 3f Slit 4 Filter 5 Ring nut 6 Code 6a Core wire 7 Rubber bush 8 Ring nut 9 Gauge lead 10 Strain element 10a Thick cylindrical part 10b Strain portion 10c Center thick rigid part 10d Force transmission rod 10e, 10f Slit 11 Pressure receiving diaphragm 12 Double type strain gauge 12a Substrate (gauge base) 12b, 12c Gauge pattern 12d Recess 12e Grid part 12f Sensitive axis 12-1-6 Double type strain gauge 13 Strain element 13a Thickness Meat cylinder part 13b Strain part 13c Step part

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[Procedure amendment]

[Submission date] July 12, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 11

[Correction method] Change

[Correction content]

FIG. 11

Claims (5)

[Claims] 1. A physical quantity is converted into an electric quantity by a strain gauge attached to a strain generating part of a strain generating body which generates a strain in response to a physical quantity such as pressure, displacement, load and acceleration, and which exhibits a resistance change corresponding to the strain. In the strain gauge type transducer, the first to fourth active gauges attached to the strain generating portion of the strain generating body are attached to positions that can be considered to be substantially the same as the first active gauge, and A fifth active gauge that can be regarded as having substantially the same strain gauge characteristics such as strain output characteristics, aging characteristics, gauge ratio and temperature characteristics of the first active gauge, and substantially the same position as the second active gauge. Strain gauge characteristics such as strain output characteristics, aging characteristics, gauge ratio and temperature characteristics of the second active gauge attached to a position that can be considered are actual. A sixth active gauge that can be considered to be qualitatively the same, and at least the third active gauge that is attached to the rigid body portion of the strain generating body that is in the vicinity of the third active gauge and that does not substantially cause strain due to the physical quantity. A first dummy gauge having a time-varying characteristic that can be regarded as substantially the same as the time-varying characteristic of the gauge, and a rigid body of the strain-generating body in the vicinity of the fourth active gauge that does not substantially cause strain due to the physical quantity. A second dummy gauge attached to the portion and having at least a time-dependent change characteristic that can be regarded as substantially the same as the time-dependent change characteristic of the fourth active gauge; and a first dummy gauge having the first to fourth active gauges. A second bridge having the fifth and sixth active gauges and the first and second dummy gauges. Forming a circuit, the first and second
A strain gauge type converter configured so that a strain output component corresponding to the physical quantity and an initial value variation component due to the change with time can be separated based on the output of the bridge circuit. 2. The pair of the first and fifth active gauges and the pair of the second and sixth active gauges are arranged on the same substrate so that their respective sensitive axes are oriented in the same direction for each pair. Strain gauges formed of the same material at the same time in close proximity to each other and used as active gauges, respectively, while the third active gauge, the fourth active gauge, the first dummy gauge, and the The second dummy gauge is a pair of gauge elements formed under substantially the same conditions as the pair of first and fifth active gauges or the pair of second and sixth active gauges. The strain gauge type transducer according to claim 1, wherein one of the pair of gauge elements is used. 3. A physical quantity is converted into an electric quantity by a strain gauge attached to a strain generating part of a strain generating body which generates a strain in response to a physical quantity such as pressure, displacement, load, acceleration, etc. and which exhibits a resistance change corresponding to the strain. In the strain gauge type transducer, the first to fourth active gauges attached to the strain generating portion of the strain generating body, and the strain due to the physical quantity in the vicinity of each of the first to fourth active gauges, First to fourth dummy gauges that have a time-dependent change characteristic that can be regarded as substantially the same as the time-dependent change characteristic of the active gauge that is attached to the rigid body portion of the flexure element that does not substantially occur and that is attached at least in pairs. A first bridge circuit is formed by the first to fourth active gauges, and a second bridge circuit is formed by the first to fourth dummy gauges. A strain gauge type characterized in that the strain output component corresponding to the physical quantity and the initial value variation output component due to the change with time can be separately detected based on the outputs of the first and second bridge circuits. converter. 4. A physical quantity is converted into an electric quantity by a strain gauge attached to a strain generating part of a strain generating body which generates a strain in response to a physical quantity such as pressure, displacement, load and acceleration, and which exhibits a resistance change corresponding to the strain. A method for detecting an initial value fluctuation amount of a strain gauge type transducer, wherein the first bridge circuit is formed with the first to fourth active gauges attached to the strain generating portion of the strain generating body, It is attached to a position that can be regarded as substantially the same position as the first active gauge, and the first active gauge is considered to have substantially the same strain gauge characteristics such as strain output characteristics, aging characteristics, gauge ratio and temperature characteristics. The fifth active gauge to be obtained is attached to a position that can be regarded as substantially the same position as the second active gauge, and the strain output of the second active gauge is provided. Characteristics, aging characteristics, gauge ratio, temperature characteristics, and other strain gauge characteristics that can be regarded as being substantially the same as the sixth active gauge, and in the vicinity of the third active gauge, distortion due to the physical quantity does not substantially occur. A first dummy gauge attached to the rigid portion of the strain generating body and having at least a time-dependent change characteristic that can be regarded as substantially the same as the time-dependent change characteristic of the third active gauge, and the vicinity of the fourth active gauge. And a second dummy gauge that is attached to the rigid body portion of the strain generating body that does not substantially generate strain due to the physical quantity and that can be regarded as at least substantially the same as the aging characteristic of the fourth active gauge. Forming a bridge circuit, and subtracting the output of the first bridge circuit from a value obtained by doubling the output of the second bridge circuit. The initial value variation detecting method of strain gage transducers and obtains the amount of variation of the initial value due to the aging. 5. The physical quantity is converted into an electric quantity by a strain gauge attached to a strain generating part of a strain generating body which generates a strain in response to a physical quantity such as pressure, displacement, load, acceleration, etc. and which exhibits a resistance change corresponding to the strain. A method for detecting an initial value fluctuation amount of a strain gauge type transducer, wherein the first bridge circuit is formed with the first to fourth active gauges attached to the strain generating portion of the strain generating body, Change over time of the active gauges that are attached in pairs to at least the rigid bodies of the strain generating body that are in the vicinity of the first to fourth active gauges and that do not substantially generate strain due to the physical quantity, and that are paired and attached. The second bridge circuit is formed by the first to fourth dummy gauges having the characteristics of change with time that can be regarded as substantially the same as the characteristics, and the second bridge circuit is formed from the output of the first bridge circuit. A method of detecting an initial value fluctuation amount of a strain gauge type converter, characterized in that an output value corresponding to the physical quantity is detected and removed by subtracting the output of the bridge circuit to detect and remove the initial value fluctuation amount. .